This invention relates to new chemical compounds, processes for their preparation, pharmaceutical formulations containing them and their use in therapy.
Inflammation is a primary response to tissue injury or microbial invasion and is characterised by leukocyte adhesion to the endothelium, diapedesis and activation within the tissue. Leukocyte activation can result in the generation of toxic oxygen species (such as superoxide anion), and the release of granule products (such as peroxidases and proteases). Circulating leukocytes include neutrophils, eosinophils, basophils, monocytes and lymphocytes. Different forms of inflammation involve different types of infiltrating leukocytes, the particular profile being regulated by the profile of adhesion molecule, cytokine and chemotactic factor expression within the tissue.
The primary function of leukocytes is to defend the host from invading organisms such as bacteria and parasites. Once a tissue is injured or infected a series of events occurs which causes the local recruitment of leukocytes from the circulation, into the affected tissue. Leukocyte recruitment is controlled to allow for the orderly destruction and phagocytosis of foreign or dead cells, followed by tissue repair and resolution of the inflammatory infiltrate. However in chronic inflammatory states, recruitment is often inappropriate, resolution is not adequately controlled and the inflammatory reaction causes tissue destruction.
There is evidence from both in vitro and in vivo studies to suggest that compounds active at the adenosine A2a receptor will have anti-inflammatory actions. The area has been reviewed by Cronstein (1994). Studies on isolated neutrophils show an A2 receptor-mediated inhibition of superoxide generation, degranulation, aggregation and adherence (Cronstein et al, 1983 and 1985; Burkey and Webster, 1993; Richter, 1992; Skubitz et al, 1988. When agents selective for the A2a receptor over the A2b receptor (eg CGS21680) have been used, the profile of inhibition appears consistent with an action on the A2a receptor subtype (Dianzani et al, 1994). Adenosine agonists may also down-regulate other classes of leukocytes (Elliot and Leonard, 1989; Peachell et al, 1989). Studies on whole animals have shown the anti-inflammatory effects of methotrexate to be mediated through adenosine and A2 receptor activation (Asako et at, 1993; Cronstein et al, 1993 and 1994). Adenosine itself, and compounds that raise circulating levels of adenosine also show anti-inflammatory effects in vivo (Green et al, 1991; Rosengren et al, 1995). In addition raised levels of circulating adenosine in man (as a result of adenosine deaminase deficiency) results in immunosuppression (Hirschom, 1993).
Certain substituted 4xe2x80x2-carboxamido and 4xe2x80x2-thioamido adenosine derivatives which are useful for the treatment of inflammatory diseases are described in International Patent Application Nos. WO94/17090, WO96/02553, WO96/02543 (Glaxo Group). Substituted 4xe2x80x2-carboxamidoadenosine derivatives useful in the treatment of dementia are described in AU 8771946 (Hoechst Japan). Substituted 4xe2x80x2-hydroxymethyl adenosine derivatives which are useful for the treatment of gastrointestinal motility disorders are described in EP-A423776 and EP-A423777 (Searle). Substituted 4xe2x80x2-hydroxymethyl adenosine derivatives which are useful as platelet aggregation inhibitors are described in BE-768925 (Takeda). 4xe2x80x2-Hydroxymethyl adenosine derivatives and 4xe2x80x2-esters thereof which are useful as anti-hypertensive agents or have other cardiovascular activity are described in U.S. Pat. No. 4,663,313, EP 139358 and U.S. Pat. No. 4,767,747 (Warner Lambert), U.S. Pat. No. 4,985,409 (Nippon Zoki) and U.S. Pat. No. 5,043,325 (Whitby Research). 4-Hydroxymethyladenosine derivatives useful in the treatment of autoimmune disorders are described in U.S. Pat. No. 5,106,837 (Scripps Research Institute). 4xe2x80x2-Hydroxymethyladenosine derivatives useful as anti-allergic agents are described in U.S. Pat. No. 4,704,381 (Boehringer Mannheim). Certain 4xe2x80x2-tetrazolylalkyl adenosine derivatives which are useful in the treatment of heart and circulatory disorders are generically described in DT-A-2621470 (Pharma-Waldhof). Other 4xe2x80x2-carboxamidoadenosine derivatives useful in the treatment of cardiovascular conditions are described in U.S. Pat. No. 5,219,840, GB 2203149 and GB 2199036 (Sandoz), WO94/02497 (US Dept. Health), U.S. Pat. No. 4,968,697 and EP 277917 (Ciba Geigy), U.S. Pat. No. 5,424,297 (Univ. Virginia) and EP 232813 (Warner Lambert).
Other 4xe2x80x2-carboxamidoadenosine derivatives lacking substitution on the purine ring in the 2-position are described in DT 2317770, DT 2213180, U.S. Pat. No. 4,167,565, U.S. Pat. No. 3,864,483 and U.S. Pat. No. 3,966,917 (Abbott Labs), DT 2034785 (Boehringer Mannheim), JP 58174322 and JP 58167599 (Tanabe Seiyaku), WO92/05177 and U.S. Pat. No. 5,364,862 (Rhone Poulenc Rorer), EP 66918 (Procter and Gamble), WO86/00310 (Nelson), EP 222330, U.S. Pat. No. 4,962,194, WO88/03147 and WO88/03148 (Warner Lambert) and U.S. Pat. No. 5,219,839, WO95/18817 and WO93/14102 (Lab UPSA). 4xe2x80x2-Hydroxymethyladenosine derivatives lacking substitution on the purine ring in the 2-position are described in WO95/11904 (Univ Florida).
4xe2x80x2-Substituted adenosine derivatives useful as adenosine kinase inhibitors are described in WO94/18215 (Gensia).
Other 4xe2x80x2-halomethyl, methyl, thioalkylmethyl or alkoxymethyl adenosine derivatives are described in EP 161128 and EP 181129 (Warner Lambert) and U.S. Pat. No. 3,983,104 (Schering). Other 4xe2x80x2-carboxamidoadenosine derivatives are described in U.S. Pat. No. 7,577,528 (NIH), WO91/13082 (Whitby Research) and WO95/02604 (US Dept Health).
Certain tetrazole containing deoxynucleotides which were found to lack anti-infective activity are described in Baker et al (1974) Tetrahedron 30, 2939-2942. Other tetrazole containing adenosine derivatives which show activity as platelet aggregation inhibitors are described in Mester and Mester (1972) Pathologie-Biologie, 20 (Suppl) 11-14.
Certain nitrile containing ribose derivatives are described in Schmidt et al (1974) Liebigs. Ann. Chem. 1856-1863.
Specifications published subsequent to the earliest priority date of this application include: WO 98/28319 (Glaxo Group Limited) describing 4xe2x80x2-substituted tetrazole 2-(purin-9-yl)-tetrahydrofuran-3,4-diol derivatives; WO 98/16539 (Novo Nordisk A/S) which describes adenosine derivatives for the treatment of myocardial and cerebral ischaemia and epilepsy; WO 98/01426 (Rhone-Poulenc Rorer Pharmaceuticals Inc.) which relates to adenosine derivatives possessing antihypertensive, cardioprotective, anti-ischaemic and antilipolytic properties; and WO 98/01459 (Novo Nordisk A/S) which describes N,9-disubstituted adenine derivatives which are substituted in the 4xe2x80x2 position by unsubstituted oxazolyl or isoxazolyl and the use of such compounds for the treatment of disorders involving cytokines in humans.
We have now found a novel group of compounds with broad anti-inflammatory properties which inhibit leukocyte recruitment and activation and which are agonists of the adenosine 2a receptor. The compounds are therefore of potential therapeutic benefit in providing protection from leukocyte-induced tissue damage in diseases where leukocytes are implicated at the site of inflammation. The compounds of the invention may also represent a safer alternative to corticosteroids in the treatment of inflammatory diseases, whose uses may be limited by their side-effect profiles.
More particularly, the compounds of this invention may show an improved profile over known A2a-selective agonists in that they generally lack agonist activity at the human A3 receptor. They may even possess antagonist activity at the human A3 receptor. This profile can be considered of benefit as A3 receptors are also found on leukocytes (eg eosinophil) and other inflammatory cells (eg mast cell) and activation of these receptors may have pro-inflammatory effects (Kohno et al, 1996; Van Schaick et al 1996). It is even considered that the bronchoconstrictor effects of adenosine in asthmatics may be mediated via the adenosine A3 receptor (Kohno et al, 1996).
Thus, according to the invention we provide compounds of formula (I): 
wherein R1 and R2 independently represent a group selected from:
(i) C3-8cycloalkyl-;
(ii) hydrogen;
(iii) aryl2CHCH2xe2x80x94;
(iv) C3-8cycloalkylC1-6alkyl-;
(v) C1-8alkyl-;
(vi) arylC1-6alkyl-;
(vii) R4R5Nxe2x80x94C1-6alkyl-;
(viii) C1-6alkyl-CH(CH2OH)xe2x80x94;
(ix) arylC1-5alkyl-CH(CH2OH)xe2x80x94;
(x) arylC1-5alkyl-C(CH2OH)2xe2x80x94;
(xi) C3-8cycloalkyl independently substituted by one or more (e.g. 1, 2 or 3) xe2x80x94(CH2)pR6 groups;
(xii) H2NC(xe2x95x90NH)NHC1-6alkyl-;
(xiii) a group of formula 
xe2x80x83or such a group in which one methylene carbon atom adjacent to X, or both if such exist, is substituted by methyl;
(xiv) xe2x80x94C1-6alkyl-OH;
(xv) xe2x80x94C1-8haloalkyl;
(xvi) a group of formula 
(xvii) aryl; and
(xviii) xe2x80x94(CH2)fSO2NHg(C1-4alkyl-)2-g or xe2x80x94(CH2)fSO2NHg(arylC1-4alkyl-)2-g;
R3 represents methyl, ethyl, xe2x80x94CHxe2x95x90CH2, n-propyl, xe2x80x94CH2CHxe2x95x90CH2, xe2x80x94CHxe2x95x90CHCH3, isopropyl, isopropenyl, cyclopropyl, cyclopropenyl, cydopropylmethyl, cyclopropenylmethyl, xe2x80x94CH(OH)CH3, xe2x80x94(CH)qhalogen, xe2x80x94(CH2)hY(CH2)iH, xe2x80x94(CH2)kZ, xe2x80x94(CH2)hCO(CH2)oH, xe2x80x94(CH2)rS(O)t(CH2)sH or xe2x80x94(CH2)kC((CH2)uH)xe2x95x90NO(CH2)vH;
Y represents O, S or N(CH2)jH;
Z represents xe2x80x94COO(CH2)tH or xe2x80x94CON(CH2)mH((CH2)nH);
a and b independently represent an integer 0 to 4 provided that a+b is in the range 3 to 5;
c, d and e independently represent an integer 0 to 3 provided that c+d+e is in the range 2 to 3;
f represents 2 or 3 and g represents an integer 0 to 2;
p represents 0 or 1;
q represents an integer 0 to 3;
h represents an integer 0 to 2;
i represents an integer 0 to 2 such that h+i is in the range 0 to 3;
j represents an integer 0 to 2 such that h+i+j is in the range 0 to 3;
k represents 0 or 1;
l represents 1 or 2, such that k+l is in the range 1 to 2;
m and n independently represent an integer 0 to 2 such that k+m+n is in the range 0 to 2;
o represents an integer 0 to 2 such that h+o is in the range 0 to 2;
r and s independently represent 1 or 2 such that r+s is in the range 2 to 3;
t represents 1 or 2;
u and v independently represent 0 or 1 such that k+u+v is in the range 0 to 1;
R4 and R5 independently represent hydrogen, C1-4alkyl, aryl, arylC1-6alkyl- or NR4R5 together may represent pyridinyl, pyrrolidinyl, piperidinyl, morpholinyl, azetidinyl, azepinyl, piperazinyl, Nxe2x80x94C1-6alkylpiperazinyl or 2-(1-methyl-1H-imidazol-4-yl)-;
R6 represents xe2x80x94OH, xe2x80x94NH2, xe2x80x94NHCOCH3 or halogen;
R7 represents hydrogen, xe2x80x94C1-6alkyl, xe2x80x94C1-6alkylaryl or xe2x80x94COC1-6alkyl;
X represents NR7, O, S, SO or SO2;
and salts and solvates thereof.
References to C1-6alkyl include references to an aliphatic hydrocarbon grouping containing 1 to 6 carbon atoms which may be straight chain or branched and may be saturated or unsaturated. References to C1-4alkyl, C1-5alkyl and C1-8alkyl may be interpreted similarly. References to alkoxy may also be interpreted similarly. Preferably these groups will be saturated.
References to aryl include references to mono- and bicyclic carbocyclic aromatic rings (e.g. phenyl, naphthyl) and heterocyclic aromatic rings containing 1-3 hetero atoms selected from N, O and S (e.g. pyridinyl, pyrimidinyl, thiophenyl, imidazolyl, quinolinyl, furanyl, pyrrolyl, oxazolyl) all of which may be optionally substituted, e.g. by C1-6alkyl, halogen, hydroxy, nitro, C1-6alkoxy, cyano, amino, SO2NH2 or xe2x80x94CH2OH.
Examples of C3-8cycloalkyl for R1 and R2 include monocyclic alkyl groups (e.g. cyclopentyl, cyclohexyl) and bicyclic alkyl groups (e.g. norbornyl such as exo-norborn-2-yl).
Examples of (aryl)2CHCH2xe2x80x94 for R1 and R2 include Ph2CHCH2xe2x80x94 or such a group in which one or both phenyl moieties is substituted, e.g. by halogen or C1-4alkyl.
Examples of C3-8cycloalkylC1-6alkyl- for R1 and R2 include ethylcyclohexyl.
Examples of C1-8alkyl for R1 and R2 include xe2x80x94(CH2)2C(Me)3, xe2x80x94CH(Et)2 and CH2xe2x95x90C(Me)CH2CH2xe2x80x94.
Examples of arylC1-6alkyl- for R1 and R2 include xe2x80x94(CH2)2Ph, xe2x80x94CH2Ph or either in which Ph is substituted (one or more times) by halogen (e.g. fluorine, iodine), amino, methoxy, hydroxy, xe2x80x94CH2OH or SO2NH2; xe2x80x94(CH2)2pyridinyl (e.g.xe2x80x94(CH2)2pyridin-2-yl) optionally substituted by amino; (CH2)2imidazolyl (eg 1H-imidazol-4-yl) or this group in which imidazolyl is N-substituted by C1-6alkyl (especially methyl).
Examples of R4R5Nxe2x80x94C1-6alkyl- for R1 and R2 include ethyl-piperidin-1-yl, ethyl-pyrrolidin-1-yl, ethyl-morpholin-1-yl, xe2x80x94(CH2)2NH(pyridin-2-yl) and xe2x80x94(CH2)2NH2.
Examples of C1-6alkyl-CH(CH2OH)xe2x80x94 for R1 and R2 include Me2CHCH(CH2OH)xe2x80x94.
Examples of arylC1-5alkyl-CH(CH2OH)xe2x80x94 for R1 and R2 include PhCH2CH(CH2OH)xe2x80x94 particularly 
Examples of aryl C1-5alkyl-C(CH2OH)2xe2x80x94 for R1 and R2 include PhCH2C(CH2OH)2xe2x80x94.
Examples of C3-8cycloalkyl independently substituted by one or more xe2x80x94(CH2)pR6 groups (eg 1, 2 or 3 such groups) for R1 and R2 include 2-hydroxy-cyclopentyl and 4-aminocyclohexyl (especially trans-4-amino-cyclohexyl).
Examples of H2NC(xe2x95x90NH)NHC1-6alkyl for R1 and R2 include H2NC(xe2x95x90NH)NH(CH2)2xe2x80x94
Examples of groups of formula 
for R1 and R2 include pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, tetrahydro-1,1-dioxide thiophen-3-yl, tetrahydropyran-4-yl, tetrahydrothiopyran-4-yl, 1-oxo-hexahydro-1.lambda.4-thiopyran-4-yl and 1,1-dioxo-hexahydro-1.lambda.6-thiopyran-4-yl, or a derivative in which the ring nitrogen is substituted by C1-6alkyl (e.g. methyl), C1-6alkylacyl (e.g. acetyl), arylC1-6alkyl- or benzyl.
Examples of xe2x80x94C1-6alkyl-OH groups for R1 and R2 include xe2x80x94CH2CH2OH.
Examples of C1-8haloalkyl for R1 and R2 include xe2x80x94CH2CH2Cl and (CH3)2ClC(CH2)3xe2x80x94.
Examples of groups of formula 
for R1 and R2 include 2-oxopyrrolidin-4-yl, 2-oxo-pyrrolidin-5-yl or a derivative in which the ring nitrogen is substituted by C1-6alkyl (e.g. methyl) or benzyl.
Examples of aryl for R1 and R2 include phenyl optionally substituted by halogen (e.g. fluorine, especially 4-fluorine).
An example of a xe2x80x94(CH2)fSO2NHg(C1-4alkyl)2-g group for R1 and R2is xe2x80x94(CH2)2SO2NHMe, and an example of a xe2x80x94(CH2)fSO2NHg(arylC1-4alkyl)2-g group for R1 and R2 is xe2x80x94(CH2)2SO2NHCH2Ph.
Examples of C1-6alkyl for R1 include methyl , of C1-6alkylaryl for R7 include benzyl and of COC1-6alkyl for R7 include COCH3.
We prefer that R1 and R2 do not both represent hydrogen.
We prefer R1 to represent C3-6cycloalkyl, aryl2CHCH2xe2x80x94, arylC1-6alkyl-, C1-6alkyl-, aryl, xe2x80x94(CH2)fSO2NHg(C1-4alkyl)2-g, tetrahydropyran-n-yl or tetrahydrothiopyran-n-yl where n is 3 or 4, C3-8cycloalkylC1-6alkyl-, hydrogen, or R4R5Nxe2x80x94C1-4alkyl- where NR4R5 together represents piperidinyl or morpholinyl.
We also prefer R1 to represent C1-6alkyl-CH(CH2OH)xe2x80x94, 1,1-dioxo-hexahydro-1.lambda.6-thiopyran-4-yl, N-acetyl-piperidin-4-yl, 1S-hydroxymethyl-2-phenylethyl, piperidin-4-yl and 1-oxo-hexahydro-1.lambda.4-thiopyran-4-yl.
We prefer R2 to represent xe2x80x94C1-6alkyl-OH, H2NC(xe2x95x90NH)NHC1-6alkyl-, R4R5NC1-6alkyl- where NR4R5 together represents pyridinyl, piperidinyl, morpholinyl or 2-(1-methyl-1H-imidazol-4-yl), arylC1-5alkylCH(CH2OH)xe2x80x94, aryl, C3-8cycloalkylC1-6alkyl-, tetrahydro-1,1-dioxide thiophen-3-yl, C3-8cycloalkyl, C1-6alkyl-CH(CH2OH)xe2x80x94, arylC1-6alkyl-, pyrrolidin-3-yl, 2-oxopyrrolidin-4-yl, 2-oxopyrrolidin-5-yl, piperidin-3-yl, aryl C1-6alkyl (e.g. benzyl), C3-8cycloalkyl independently substituted by one or more (e.g. 1, 2 or 3) xe2x80x94(CH2)pR6 groups, or piperidin-4-yl in which the ring nitrogen is optionally substituted by C1-6alkyl.
We also prefer R2 to represent C1-8alkyl or R4R5NC1-6alkyl- wherein R4 and R5 independently represent hydrogen or aryl or R4R5N together represents pyrrolidinyl.
When R3 represents halogen, we prefer it to represent bromine or chlorine, especially bromine.
We prefer R3 to represent methyl, ethyl or n-propyl.
We also prefer R3 to represent xe2x80x94CHxe2x95x90NOH, cyclopropyl, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, xe2x80x94CH2OH, xe2x80x94CH(OH)CH3 or halogen.
More preferably R3 represents methyl, ethyl, n-propyl, xe2x80x94CH2OH, xe2x80x94CH(OH)CH3, xe2x80x94CHxe2x95x90NOH or halogen.
We particularly prefer R3 to represent methyl, ethyl, xe2x80x94CH2OH or xe2x80x94CH(OH)CH3, more particularly methyl, ethyl or xe2x80x94CH2OH, especially ethyl or xe2x80x94CH2OH, most especially ethyl.
We particularly prefer R4 and R5 independently to represent hydrogen, C1-6alkyl, aryl, arylC1-6alkyl- or NR4R5 together may represent pyrrolidinyl, piperidinyl, morpholinyl, azetidinyl, azepinyl, piperazinyl or Nxe2x80x94C1-6alkylpiperazinyl.
We more particularly prefer R4 and R5 independently to represent hydrogen, C1-6alkyl or aryl or NR4R5 together to represent pyrrolidinyl, piperidinyl, morpholinyl, azetidinyl, azepinyl, piperazinyl or N-methylpiperazinyl.
We prefer that p represents 0. We prefer that R6 represents OH or NH2 especially OH.
We prefer that q represents 0 or 1, preferably 0. We prefer that Y represents O.
We prefer that Z represents xe2x80x94COOCH3. We prefer that the group xe2x80x94(CH2)hY(CH2)iH represents xe2x80x94(CH2)1-2OH. We prefer that k represents 0. We prefer that u and v represent 0. We prefer that r and s represent 1. We prefer that the group xe2x80x94(CH2)hCO(CH2)oH represents xe2x80x94COCH3. We prefer that I represents 1.
We prefer that a and b both represent 2. We prefer X to represent NR7, O, S or SO2, particularly O or S.
We prefer that c represents 0 and either d represents 2 and e represents 0 or d represents 1 and e represents 1.
We prefer R7 to represent hydrogen, C1-6alkyl, C1-6alkylaryl or xe2x80x94COCH3, particularly hydrogen, benzyl or xe2x80x94COCH3, especially hydrogen.
We prefer R3 to represent methyl, ethyl or n-propyl and R7 to represent hydrogen, xe2x80x94C1-6alkyl, xe2x80x94C1-6alkylaryl or xe2x80x94COCH3.
We particularly prefer R1 to represent C4-7cycloalkyl (particularly cyclopentyl), Ph2CHCH2xe2x80x94, PhCH2CH2xe2x80x94, C4-7alkyl, particularly xe2x80x94(CH2)2C(Me)3 or xe2x80x94CH(Et)2, a phenyl group substituted by both an xe2x80x94OH and a halogen group (e.g. fluorine) (e.g. 3-fluoro-4-hydroxy-phenyl), xe2x80x94(CH2)2SO2NHMe, or tetrahydropyran-n-yl or tetrahydrothiopyran-n-yl where n is 4.
We also particularly prefer R1 to represent hydrogen, 1S-hydroxymethyl-2-methylpropyl, 3-iodophenylmethyl, cyclohexylethyl-, benzyl, 1,1-dioxo-hexahydro-1.lambda.6-thiopyran-4-yl, N-acetyl-piperidin-4-yl, 1S-hydroxymethyl-2-phenylethyl, piperidin-4-yl and 1-oxo-hexahydro-1.lambda.4-thiopyran-4-yl.
Most especially preferred R1 is xe2x80x94CH2CHPh2, xe2x80x94CH(Et)2 or phenylethyl.
We particularly prefer R2 to represent xe2x80x94C2-4alkyl-OH, H2NC(xe2x95x90NH)NHC2-4alkyl or R4R5Nxe2x80x94C1-4alkyl- where NR4R5 together represents pyridinyl, piperidinyl, morpholinyl or 2-(1-methyl-1H-imidazol-4-yl).
We also particularly prefer R2 to represent 2-(1-methyl-1H-imidazol-4-yl)ethyl, pyridin-2-ylethyl, 1S-hydroxymethyl-2-phenylethyl, pyridin-2-yl-NH(CH2)2xe2x80x94, 4-(H2NSO2)-phenylethyl, trans-4-aminocyclohexyl, trans-4-(CH3CONH)-cyclohexyl, pyrrolidin-3-yl, 3,4-dimethoxyphenylethyl, N-benzyl-pyrrolidin-3-yl-, pyrrolidin-1-ylethyl, aminoethyl or ethyl.
We especially prefer R2 to represent piperidin-1-ylethyl, morpholin-1-ylethyl, xe2x80x94(CH2)2OH, 2-(1-methyl-1H-imidazol-4-yl)ethyl, H2NC(xe2x95x90NH)NHethyl, pyridin-2-ylethyl, 1S-hydroxymethyl-2-phenylethyl, pyridin-2-yl-NH(CH2)2xe2x80x94, 4-(H2NSO2)-phenylethyl, trans-4-aminocyclohexyl, trans-4-(CH3CONH)-cyclohexyl, pyrrolidin-3-yl, 3,4-dimethoxyphenylethyl, N-benzyl-pyrrolidin-3-yl-, pyrrolidin-1-ylethyl, aminoethyl or ethyl.
Most especially preferred R2 is piperidin-1-ylethyl or 2-(1-methyl-1H-imidazol-4-yl)ethyl.
The most preferred compounds of formula (I) are
(2R,3R,4S,5S)-2-[6-(2,2-Diphenyl-ethylamino)-2-(2-piperidin-1-yl-ethylamino)-purin-9-yl]-5-(3-ethyl-isoxazol-5-yl)-tetrahydro-furan-3,4-diol;
(2R,3R,4S,5S)-2-(3-Ethyl-isoxazol-5-yl)-5-[6-phenethylamino-2-(2-piperidin-1-yl-ethylamino)-purin-9-yl]-tetrahydro-furan-3,4-diol;
(2S,3S,4R,5R)-2-(3-Ethyl-isoxazol-5-yl)-5-[6-(1-ethyl-propylamino)-2-(2-piperidin-1-yl-ethylamino)-purin-9yl]-tetrahydro-furan-3,4-diol;
(2R,3R,4S,5S)-2-[6-(1-Ethyl-propylamino)-2-(2-piperidin-1-yl-ethylamino)-purin-9-yl]-5-[3-(1-hydroxy-ethyl)-isoxazol-5-yl]-tetrahydro-furan-3,4-diol;
(2R,3R,4S,5S)-2-{6-(1-Ethyl-propylamino)-2-[2-(1-methyl-1H-imidazol-4-yl)-ethylamino]-purin-9-yl}5-(3-methyl-isoxazol-5-yl)-tetrahydro-furan-3,4-diol;
(2R,3R,4S,5S)-2-{6-(1-Ethyl-propylamino)-2-[2-(1-methyl-1H-imidazol-4-yl)-ethylamino]-purin-9-yl}-5-(3-hydroxymethyl-isoxazol-5-yl)-tetrahydro-furan-3,4-diol;
and salts and solvates thereof.
The representation of formula (I) indicates the absolute stereochemistry. When sidechains contain chiral centres the invention extends to mixtures of enantiomers (including racemic mixtures) and diastereoisomers as well as individual enantiomers. Generally it is preferred to use a compound of formula (I) in the form of a purified single enantiomer.
We also provide a process for preparation of compounds of formula (I) which comprises:
(a) reacting a corresponding compound of formula (II) 
wherein L represents a leaving group e.g. halogen, particularly chlorine or a protected derivative thereof
with a compound of formula R2NH2 or a protected derivative thereof;
(b) reacting a corresponding compound of formula (III) 
xe2x80x83with a compound of formula (IV) 
xe2x80x83wherein L represents a leaving group or a protected derivative thereof;
(c) converting one compound of formula (I) to another compound of formula (I); or
(d) deprotecting a compound of formula (I) which is protected;
and where desired or necessary converting a compound of formula (I) or a salt thereof into another salt thereof.
The reaction of process (a) will generally be carried out on heating the reagents to a temperature of 50xc2x0 C.-150xc2x0 C. in the presence of an inert solvent such as DMSO. The compound of formula (II) will generally be used in a form which the two hydroxyl groups are protected e.g. with acetyl groups.
In process (b), we prefer to use the compound of formula (IV) when the ribose 2- and 3-hydroxyl groups are protected for example by acetyl. Leaving group L may represent OH but will preferably represent C1-6alkoxy (e.g. methoxy or ethoxy) an ester moiety (e.g. acetyloxy or benzoyloxy) or halogen. The preferred group L is acetyloxy. The reaction may be formed by combining the reactants in an inert solvent such as MeCN in the presence of a Lewis Acid (e.g. TMSOTf) and DBU.
Examples of process (c) include converting compounds of formula (I) wherein R3 represents halogen (e.g. Br) to a corresponding compound of formula (I)
wherein R3 represents alkyl or a protected alcohol for example by treatment with a corresponding metallic reagent such as a magnesium or zinc halide optionally catalysed by another metal such as Pd in the presence of ligands such as PPh3. Compounds of formula (I) wherein R3 represents halogen (e.g. Br) may be converted to corresponding compounds of formula (I) wherein R3 represents alkoxy by treatment with the corresponding metal alkoxide (eg KOCH3) in the corresponding alcoholic solvent.
In process (d) examples of protecting groups and the means for their removal can be found in T W Greene xe2x80x9cProtective Groups in Organic Synthesisxe2x80x9d (J Wiley and Sons, 1991). Suitable hydroxyl protecting groups include alkyl (e.g. methyl), acetal (e.g. acetonide) and acyl (e.g. acetyl or benzoyl) which may be removed by hydrolysis, and arylalkyl (e.g. benzyl) which may be removed by catalytic hydrogenolysis. Suitable amine protecting groups include sulphonyl (e.g. tosyl), acyl e.g. benzyloxycarbonyl or t-butoxycarbonyl) and arylalkyl (e.g. benzyl) which may be removed by hydrolysis or hydrogenolysis as appropriate.
We also provide a further process (e) for preparing compounds of formula (I) which comprises reacting a corresponding compound of formula (IIa): 
wherein L represents a leaving group eg. halogen, particularly chlorine or a protected derivative thereof, with a compound of formula R1NH2 or a protected derivative thereof.
This reaction may be performed under conditions analogous to those described above for process (a).
Suitable salts of the compounds of formula (I) include physiologically acceptable salts such as acid addition salts derived from inorganic or organic acids, for example hydrochlorides, hydrobromides, sulphates, phosphates, acetates, benzoates, citrates, succinates, lactates, tartrates, fumarates, maleates, 1-hydroxynathanoate, methanesulphonate, and if appropriate, inorganic base salts such as alkali metal salts, for example sodium salts. Other salts of the compounds of formula (I) include salts which are not physiologically acceptable but may be useful in the preparation of compounds of formula (I) and physiologically acceptable salts thereof. Examples of such salts include trifluoroacetates and formates.
Examples of suitable solvates of the compounds of formula (I) include hydrates.
Acid-addition salts of compounds of formula (I) may be obtained by treating a free-base of formula (I) with an appropriate acid.
The compounds of formula (II) may be prepared by a process which comprises reacting a compound of formula (V) 
wherein L1 and L2 independently represent a leaving group, especially halogen (eg chlorine) or a protected derivative thereof
with a compound of formula R1NH2.
This reaction will preferably be performed in the presence of a base such as an amine base (e.g. diisopropyl ethylamine) in a solvent such as DMF or an alcohol (e.g. isopropanol) at elevated temperature (e.g. 50xc2x0 C.).
The compounds of formula (V) may be prepared by a process which comprises reacting a compound of formula (IV) with a purine derivative such as dihalopurine especially 2,6 dichloropurine under conditions analogous to those described above in process (b).
Compounds of formula (II) may be prepared by a route analogous to process (b) also.
The compounds of formula (IV) or a protected derivatives thereof may be prepared from a compound of formula (VI) 
by a process comprising treating the compound of formula (VI) with trifluoroacetic acid in water followed by acetic anhydride in a solvent such as pyridine, Et3N, DCM or a combination of these.
Compounds of formula (IV) in which L represents halogen may be prepared from the corresponding 5-alcohol or a 5-ester such as the acetate. Reaction will generally occur on treatment with anhydrous HCl or HBr. 5-Iodides may be prepared directly on treatment with trimethylsilyliodide and 5-fluorides may be prepared on treatment with DAST. An inert solvent, e.g. diethylether, DCM, THF or CCl4 will generally be suitable.
The compound of formula (VI) may be prepared following Scheme 1. 
General conditions for Stages 1-5 will be known to persons skilled in the art. It will also be appreciated that the reagents and conditions set out in Scheme 1 are example conditions and alternative reagents and alternative conditions for achieving the same chemical transformation involving modification of protecting groups may be known to persons skilled in the art. For example an alternative alcohol e.g. a C1-6alkyl alcohol may be used in Stage 1 to give a different C1-6alkyloxy leaving group in compounds of formula (VI).
Certain compounds of formula (IV), in which L represents OMe may also be prepared following Scheme 1A: 
When R3 represents xe2x80x94CH2OH, suitable conditions for step (b) comprise treatment with a suitable lithium reagent, such as nBuLi/HCxe2x89xa1CCH2OTHP followed by BF3.Et2O in the presence of an inert solvent eg. THF at low temperatures (typically xe2x88x9278xc2x0 C.). When R3 represents alkyl, particularly ethyl, the transformation may be performed using a Grignard reagent, eg. MgBrCxe2x89xa1Cxe2x80x94CH2CH3 in an inert solvent eg. THF, followed by work-up.
Compounds of formula (III) may be prepared, for example, following Scheme 2: 
Compounds of formula (II) may also be prepared following Scheme 3: 
Preferred leaving group L is halogen, especially chlorine.
General conditions for Stages 1-4 will be known to persons skilled in the art. It will also be appreciated that the reagents and conditions set out in Scheme 2 are example conditions and alternative reagents and alternative conditions for achieving the same chemical transformation involving modification (or absence) of protecting groups may be known to persons skilled in the art.
The conditions of Scheme 3 Stages 1-4 may also be suitable for forming the substituted isoxazolyl ring of compounds of formula (IV), (V) and (VI).
Compounds of formula (II) may also be prepared by a process which comprises reacting a compound of formula (XI) 
wherein L is a leaving group such as halogen, especially chlorine or a protected derivative thereof,
with a nitrile oxide derived from a compound of formula R3CH2NO2. Suitable conditions are described above for Scheme 1, Stage 5. We prefer to use the compound of formula (XI) as a derivative in which both hydroxy groups are protected as the acetyl ester.
Compounds of formula (XI) (especially those wherein L represents chlorine) may be prepared from the corresponding dichloropurine derivatives which may in turn be prepared from the compound which is the product of Scheme 1, Stage 4 using conventional methods or methods described herein.
Compounds of formula (II) may also be prepared by a process comprising reacting a compound of formula (XI), or a protected derivative thereof, with a compound of formula (XII). 
wherein Hal represents halogen, eg chlorine or bromine.
This reaction may proceed on combining the reagents in the presence of a mild base eg NaHCO3 or triethylamine in the presence of a polar organic solvent system such as ethylacetate/water or DMF.
Compounds of formula (II) in which R3 represents CH(OH)CH3 may be prepared by reduction of the corresponding methylketone (using conventional reagents such as NaBH4) The corresponding methylketone can be prepared from a derivative compound of formula (XII) in which R3 represents COCH3.
Compounds of formula (IIa) may be prepared by reaction of a compound of formula (XIII): 
with a compound of formula (IV) under analogous conditions to those described for main process (b) above.
Compounds of formula (XIII) in which L represents chlorine can be prepared by reacting 2-bromoxanthine with R2NH2 followed by POCl3. Derivatives of compounds of formula (XIII) containing a different leaving group, L may be prepared by an analogous method.
Compounds of formula R1NH2, R2NH2 and R3CH2NO2 are either known or may be prepared by conventional methods known per se.
Compounds of formula (VII) may be prepared following methods described in International Patent Application No. WO94/17090.
Compounds of formula R1xe2x80x94xe2x89xa1xe2x80x94MgCl may be prepared by conventional methods known to those skilled in the art. For example, they may be prepared by reacting methyl magnesium chloride with a terminal acetylene compound at 0-25xc2x0 C. in THF.
Compounds of formula (XII) are either known or may be prepared by conventional methods known per se.
As indicated above, certain intermediates may be used in a protected form and examples of such protecting groups and methods of deprotection are described in main process (d) above.
The potential for compounds of formula (I) to inhibit leukocyte function may be demonstrated, for example, by their ability to inhibit superoxide (O2xe2x80x94) generation from neutrophils stimulated with chemoattractants such as N-formylmethionyl-leucyl-phenylalanine (fMLP). Accordingly, compounds of formula (I) are of potential therapeutic benefit in providing protection from leukocyte-induced tissue damage in diseases where leukocytes are implicated at the site of inflammation.
Examples of disease states in which the compounds of the invention have potentially beneficial anti-inflammatory effects include diseases of the respiratory tract such as adult respiratory distress syndrome (ARDS), bronchitis (including chronic bronchitis), cystic fibrosis, asthma (including allergen-induced asthmatic reactions), emphysema, rhinitis and septic shock. Other relevant disease states include diseases of the gastrointestinal tract such as intestinal inflammatory diseases including inflammatory bowel disease (e.g. Crohn""s disease or ulcerative colitis), Helicobacter-pylori induced gastritis and intestinal inflammatory diseases secondary to radiation exposure or allergen exposure, and non-steroidal anti-inflammatory drug-induced gastropathy. Furthermore, compounds of the invention may be used to treat skin diseases such as psoriasis, allergic dermatitis and hypersensitivity reactions and diseases of the central nervous system which have an inflammatory component eg Alzheimer""s disease and multiple sclerosis.
Further examples of disease states in which compounds of the invention have potentially beneficial effects include cardiac conditions such as peripheral vascular disease, post-ischaemic reperfusion injury and idiopathic hypereosinophilic syndrome.
Compounds of the invention which inhibit lymphocyte function may be useful as immunosuppressive agents and so have use in the treatment of auto-immune diseases such as rheumatoid arthritis and diabetes.
Compounds of the invention may also be useful in inhibiting metastasis and promoting wound healing.
It will be appreciated by those skilled in the art that reference herein to treatment extends to prophylaxis as well as the treatment of established conditions.
As mentioned above, compounds of formula (I) are useful in human or veterinary medicine, in particular as anti-inflammatory agents.
There is thus provided as a further aspect of the invention a compound of formula (I) or a physiologically acceptable salt or solvate thereof for use in human or veterinary medicine, particularly in the treatment of patients with inflammatory conditions who are susceptible to leukocyte-induced tissue damage.
According to another aspect of the invention, there is provided the use of a compound of formula (I) or a physiologically acceptable salt or solvate thereof for the manufacture of a medicament for the treatment of patients with inflammatory conditions who are susceptible to leukocyte-induced tissue damage.
In a further or alternative aspect there is provided a method for the treatment of a human or animal subject with an inflammatory condition who is susceptible to leukocyte-induced tissue damage, which method comprises administering to said human or animal subject an effective amount of a compound of formula (I) or a physiologically acceptable salt or solvate thereof.
The compounds according to the invention may be formulated for administration in any convenient way, and the invention therefore also includes within its scope pharmaceutical compositions for use in anti-inflammatory therapy, comprising a compound of formula (I) or a physiologically acceptable salt or solvate thereof together, if desirable, with one or more physiologically acceptable carriers or excipients.
There is also provided a process for preparing such a pharmaceutical formulation which comprises mixing the ingredients.
The compounds according to the invention may, for example, be formulated for oral, buccal, parenteral, topical or rectal administration, preferably for parenteral or topical (e.g. by aerosol) administration. The most preferred route is by topical administration to the lung (eg. by aerosol or dry powder composition).
Tablets and capsules for oral administration may contain conventional excipients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, mucilage of starch, cellulose or polyvinyl pyrrolidone; fillers, for example, lactose, microcrystalline cellulose, sugar, maize- starch, calcium phosphate or sorbitol; lubricants, for example, magnesium stearate, stearic acid, talc, polyethylene glycol or silica; disintegrants, for example, potato starch, croscarmellose sodium or sodium starch glycollate; or wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in the art Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, for example, sorbitol syrup, methyl cellulose, glucose/sugar syrup, gelatin, hydroxymethyl cellulose, carboxymethyl cellulose, aluminium stearate gel or hydrogenated edible fats; emulsifying agents, for example, lecithin, sorbitan mono-oleate or acacia; non-aqueous vehicles (which may include edible oils), for example almond oil, fractionated coconut oil, oily esters, propylene glycol or ethyl alcohol; or preservatives, for example, methyl or propyl p-hydroxybenzoates or sorbic acid. The preparations may also contain buffer salts, flavouring, colouring and/or sweetening agents (e.g. mannitol) as appropriate.
For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.
The compounds may also be formulated as suppositories, e.g. containing conventional suppository bases such as cocoa butter or other glycerides.
The compounds according to the invention may also be formulated for parenteral administration by bolus injection or continuous infusion and may be presented in unit dose form, for instance as ampoules, vials, small volume infusions or pre-filled syringes, or in multi-dose containers with an added preservative. The compositions may take such forms as solutions, suspensions, or emulsions in aqueous or non-aqueous vehicles, and may contain formulatory agents such as anti-oxidants, buffers, antimicrobial agents and/or tonicity adjusting agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile, pyrogen-free water, before use. The dry solid presentation may be prepared by filling a sterile powder aseptically into individual sterile containers or by filling a sterile solution aseptically into each container and freeze-drying.
By topical administration as used herein, we include administration by insufflation and inhalation. Examples of various types of preparation for topical administration include ointments, creams, lotions, powders, pessaries, sprays, aerosols, capsules or cartridges for use in an inhaler or insufflator, solutions for nebulisation or drops (e.g. eye or nose drops).
Ointments and creams may, for example, be formulated with an aqueous or oily base with the addition of suitable thickening and/or gelling agents and/or solvents. Such bases may thus, for example, include water and/or an oil such as liquid paraffin or a vegetable oil such as arachis oil or castor oil or a solvent such as a polyethylene glycol. Thickening agents which may be used include soft paraffin, aluminium stearate, cetostearyl alcohol, polyethylene glycols, microcrystalline wax and beeswax.
Lotions may be formulated with an aqueous or oily base and will in general also contain one or more emulsifying agents, stabilising agents, dispersing agents, suspending agents or thickening agents.
Powders for external application may be formed with the aid of any suitable powder base, for example, talc, lactose or starch. Drops may be formulated with an aqueous or non-aqueous base also comprising one or more dispersing agents, solubilising agents or suspending agents.
Spray compositions may be formulated, for example, as aqueous solutions or suspensions or as aerosols delivered from pressurised packs, with the use of a suitable propellant, e.g. dichlorodifluoromethane, trichlorofluoromethane, dichlorotetra-fluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1,2-tetrafluorethane, carbon dioxide or other suitable gas.
Intranasal sprays may be formulated with aqueous or non-aqueous vehicles with the addition of agents such as thickening agents, buffer salts or acid or alkali to adjust the pH, isotonicity adjusting agents or anti-oxidants.
Capsules and cartridges of for example gelatin, or blisters of for example laminated aluminium foil, for use in an inhaler or insufflator may be formulated containing a powder mix of a compound of the invention and a suitable powder base such as lactose or starch.
Solutions for inhalation by nebulation may be formulated with an aqueous vehicle with the addition of agents such as acid or alkali, buffer salts, isotonicity adjusting agents or antimicrobials. They may be sterilised by filtration or heating in an autoclave, or presented as a non-sterile product.
The pharmaceutical compositions according to the invention may also be used in combination with other therapeutic agents, for example anti-inflammatory agents (such as corticosteroids (eg fluticasone propionate, beclomethasone dipropionate, mometasone furoate, triamcinolone acetonide or budesonide) or NSAIDs (eg sodium cromoglycate)) or beta adrenergic agents (such as salmeterol, salbutamol, formoterol, fenoterol or terbutaline and salts thereof) or antiinfective agents (eg antibiotics, antivirals).
The invention thus provides, in a further aspect, a combination comprising a compound of formula (I) or a physiologically acceptable salt or solvate thereof together with another therapeutically active agent, for example an anti-inflammatory agent such as a corticosteroid or NSAID.
The combination referred to above may conveniently be presented for use in the form of a pharmaceutical formulation and thus pharmaceutical formulations comprising a combination as defined above together with a pharmaceutically acceptable carrier thereof represent a further aspect of the invention.
The individual components of such combinations may be administered either sequentially or simultaneously in separate or combined pharmaceutical formulations. Appropriate doses of known therapeutic agents will be readily appreciated by those skilled in the art.
Compounds of the invention may conveniently be administered in amounts of, for example, 0.01 to 500 mg/kg body weight, preferably 0.01 to 100 mg/kg body weight, 1 to 4 times daily. The precise dose will of course depend on the age and condition of the patient and the particular route of administration chosen.
Certain intermediate compounds described herein are new and these are also provided as an aspect of the invention.
The compounds of the invention have the advantage that they may be more efficacious, show greater selectivity, have fewer side effects, have a longer duration of action, be more bioavailable by the preferred route, show less systemic activity when administered by inhalation or have other more desirable properties than similar known compounds.
In particular the compounds of the invention have the advantage that they may show greater selectivity for the adenosine 2a receptor subtype over other adenosine receptor subtypes (especially the A1 and A3 receptor subtypes) than hitherto known compounds.
Compounds of the invention may be tested for in vitro and in vivo biological activity in accordance with the following screens:
(1) Agonist Activity Against Adenosine 2a, Adenosine 1 and Adenosine 3 Receptor Subtypes.
Agonist selectivity of compounds against other human adenosine receptors is determined using Chinese hamster ovary (CHO) cells transfected with the gene for the relevant human adenosine receptor following a method based on that of Castanon and Spevak, 1994. The CHO cells are also transfected with cyclic AMP response elements promoting the gene for secreted placental alkaline phosphatase (SPAP) (Wood, 1995). The effect of test compounds may be determined by their effects on basal levels of cAMP (A2a) or on forskolin-enhanced cAMP (A1 and A3) as reflected by changes in levels of SPAP. EC50 values for compounds may then be determined as a ratio to that of the non-selective agonist N-ethyl carboxamide adenosine (NECA).
(2) Antigen-induced Lung Eosinophil Accumulation in Sensitised Guinea Pigs.
Ovalbumin sensitised guinea pigs are dosed with mepyramine (1 mg/kg ip) to protect against anaphylactic bronchospasm. A compound of the invention is then given by the inhaled route (30 min breathing of an aerosol of the compound) immediately prior to ovalbumin challenge (30 min breathing of an aerosol generated from a 50 ug/ml solution of ovalbumin). Twenty four hours after challenge, the guinea pigs are killed and the lungs lavaged. Total and differential leukocyte counts are then obtained for the bronchoalveolar lavage fluid and the dose of test compound giving a 50% reduction in eosinophil accumulation (ED50) is determined (Sanjar et al. 1992).
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The invention is illustrated by the following Examples: